1. Field of the Invention
This invention relates to an automatic tuning device for automatically tuning an output tone signal from one or more voltage controlled oscillators on the basis of an error signal with respect to a designated value.
2. Description of the Prior Art
For an automatic tuning device employed in a synthesizer of an electronic musical instrument, there have heretofore been proposed a variety of systems of automatically tuning an output tone signal from a voltage controlled oscillator. Those of the conventional systems which employ an analog signal processing method have the defect that the device is inevitably bulky and expensive. A system using a digital processing method is a phase lock loop, but has the disadvantage that, in the case of tuning several synthesizers, if different foot ratios are selected for the individual synthesizers, a frequency divider must be inserted for each foot ratio.